The present invention generally relates to master disks for transferring magnetic patterns and magnetic recording media, and, more particularly, to a master disk for transferring a predetermined magnetic pattern onto a magnetic recording medium, such as a magnetic disk, mounted on a magnetic recording device generally employed as an external memory of a computer.
In recent years, magnetic recording devices have larger capacities and higher recording densities. With this trend, there is an increasing demand for reasonably priced magnetic recording media with large capacities that can record a larger volume of information and can shorten the access time for reproduction. To realize such a large-capacity magnetic recording medium, a so-called tracking servo technique has been conventionally employed so that a magnetic head can accurately perform a scanning operation on narrow tracks.
In a large-capacity magnetic recording medium, a magnetic pattern according to a signal such as a tracking servo signal is “pre-formatted” at certain intervals in each one circle on a magnetic disk, for instance. A magnetic head reads the magnetic pattern, and then corrects the position of the magnetic head itself so as to perform a scanning operation on the tracks with high precision.
In the prior art, a magnetic recording medium having the above magnetic pattern is produced by performing a recording operation on each one track of each one disk, using a servo information recording device designed specially for magnetic recording media. Such a servo information recording device requires a mechanism for positioning a recording head with high precision, and therefore is expensive. Furthermore, a longer time is required for recording a magnetic pattern on a magnetic recording medium having a larger capacity. As a result, the magnetic pattern recording procedure takes a large proportion of the entire production process for producing the large-capacity magnetic recording medium, and leads to a higher production cost.
To solve the above problems, a technique for transferring a magnetic pattern onto a magnetic recording medium from a disk (or a “master disk”) having magnetic layers patterned in accordance with the magnetic pattern has been suggested, instead of the conventional technique of recording a magnetic pattern onto each one track.
According to this transfer technique using the master disk, the magnetic body is brought into contact with a magnetic recording medium to be pre-formatted, so that the magnetic layers are excited by an external magnetic field supplied to the magnetic recording medium. In this manner, a magnetic recording medium having a predetermined magnetic pattern can be produced in a short time. Thus, the production procedures can be simplified, and the production costs can be lowered.
FIG. 1 shows a magnetic pattern transfer device 100 that employs a conventional master disk. A master disk 110 is placed on a magnetic recording medium 120, and a magnetic field 105 is supplied from a magnet 101 that serves as a magnetic field generator. The master disk 110 has magnetic layers 111 at locations corresponding to a magnetic pattern predetermined by a signal such as a servo signal. In FIG. 1, the magnetic layers 111 are excited by the magnetic field 105, and, as a result, the pattern formed by the magnetic layers 111 is transferred as a transferred pattern 121 onto the magnetic recording medium 120.
In the magnetic pattern transfer device 100 shown in FIG. 1, the magnetic layers 111 of the master disk 110 are brought toward the recording medium 120 close enough to supply the magnetic field 105, so that the magnetic pattern in the magnetic body 110 can be transferred onto the magnetic recording medium 120 with high precision. To achieve this, it is essential that the lower surface 110A of the master disk 110 should be tightly brought into contact with the upper surface 120A of the magnetic recording medium 120.
The lower surface 110A of the conventional master disk 110 to be brought into contact with the magnetic recording medium 120 is flat, and generally so is the upper surface 120A of the magnetic recording medium 120. Because of this, when a foreign matter DAS exists between the master disk 110 and the magnetic recording medium 120, as shown in FIG. 2, the contact between the master disk 110 and the magnetic recording medium 120 cannot be good enough to achieve precise pattern transfer.
Generally, it is difficult to achieve contact between two flat surfaces, with air or moisture existing in between. On the other hand, once two flat surfaces are brought into contact, it also becomes difficult to separate the two flat surfaces from each other, due to the surface tension of the air or moisture.